1. Technical Field
The present invention relates to an oxide superconducting conductor, and its production method, that can be used in fields such as superconducting power cables, superconducting magnets, superconductive energy storage, superconducting power generation systems, medical MRI systems and superconducting current leads.
2. Background Art
Known methods of producing oxide superconducting conductors of the prior art include solid phase methods such as the powder-in-tube (PIT) method in which a powder of an oxide superconductor, or a mixed powder of a composition that is able to become an oxide superconductor by heat treatment, is pressed into the shape of a cylindrical column, inserted into a silver tube and then drawn or rolled followed by a heat treatment step to form a wire material, as well as film deposition methods in which an oxide superconductor layer is continuously formed on a long base material such as metal tape by a vapor phase method such as laser deposition or sputtering.
As shown in FIG. 11, the structure of oxide superconducting conductors produced by a vapor phase method such as laser deposition or CVD is widely known to consist of the formation of a YBaCuO-based oxide superconductor layer 193 formed on the upper surface of a base material 191 composed of a metal such as Ag, and the formation of a surface protective layer 195 composed of Ag on this oxide superconductor layer 193.
In order to obtain superior superconductor characteristics in such oxide superconducting conductors produced by a vapor phase method such as laser deposition of CVD, it is important to realize biaxial orientation (in-plane orientation) of oxide superconductor layer 193 produced on base material 191. In order to accomplish this, it is preferable that the lattice constant of base material 191 approach the lattice constant of oxide superconductor layer 193, and that the crystal grains that compose the surface of base material 191 be uniformly arranged in the manner of pseudo single crystals.
Therefore, in order to solve this problem, as shown in FIG. 12, various attempts have been made to produce an oxide superconducting conductor having superior superconductivity by forming a polycrystalline intermediate layer 192 such as YSZ (yttrium-stabilized zirconium) using a sputtering device on the upper surface of a metal base material 191 such as hastelloy tape, forming an oxide superconductor layer 193 such as YBaCuO on this polycrystalline intermediate layer 192, and then additionally forming a stabilizing layer 194 of Ag on the oxide superconductor layer 193. Alternatively, studies have also been conducted on Ag base materials in which a texture is formed by rolling and heat treatment, and Ni base materials in which a texture is formed by rolling and heat treatment followed additionally by the formation of an oxide intermediate layer.
Among these, since Ag is the only metal material that has little reactivity with oxide superconductor layer 193 and allows oxide superconductor layer 193 to be formed directly on base material 191, while also having the characteristics of being non-magnetic and having low resistance, a wire material structure can be realized in which base material 191 itself also functions as the stabilizing layer.
Examples of materials that have been developed as Ag base materials in the form of tape that form a texture by rolling and heat treatment include Ag {100} less than 001 greater than  having surface {100} for the surface of the base material and a cube texture in which  less than 001 greater than  is preferentially oriented in the lengthwise direction, or Ag {110} less than 110 greater than  having surface (110) for the surface of the base material and a cube texture in which  less than 110 greater than  is preferentially oriented in the lengthwise direction, and in consideration of lattice matching with a YBaCuO-based oxide superconductor layer, the Ag {110} less than 110 greater than  oriented Ag base material is the more promising.
In an oxide superconducting conductor in which oxide superconductor layer 193 is formed on a polycrystalline intermediate layer 192 as shown in FIG. 12, the surface formed by oxide superconductor layer 193 has superior smoothness and in-plane orientation due to the action of this polycrystalline intermediate layer 192, thereby allowing the obtaining of an oxide superconductor layer 193 having a satisfactory in-plane orientation, and has recently been confirmed to enable a high Jc value of 1,000,000 A/cm2 or higher. In addition, since hastelloy is used as the metal tape, wire materials can be produced having adequate strength. However, since base materials equipped with this polycrystalline intermediate layer 192 require the use of sophisticated and expensive technology in the form of ion beam sputtering for their film deposition, at present, these base materials are only able to be produced at the rate of about 1 meter per hour, while also having the disadvantage of extremely high production costs.
On the other hand, in an oriented Ag base material using a rolling texture of Ag, although the productivity of the base material can be increased and production costs are comparatively low making this promising, there are hardly any reports of obtaining a high Jc value of 100,000 A/cm2 or more using this oriented Ag base material, thereby resulting in the problem of insufficient superconductor characteristics. This is thought to be due to impaired continuity of the oxide superconductor layer caused by irregularities in the crystal grain boundary of the Ag base material. In addition, in the case of using an Ag base material, since Ag itself is an extremely soft metal and is softened even more as a result of being heated to a high temperature during deposition of the oxide superconductor layer, in order to apply oxide superconductors using an Ag base material to wire materials and so forth, it is necessary to solve the problem of strength.
The object of the present invention is to provide an oxide superconducting conductor having superior strength and superconductor characteristics by using a base material consisting mainly of Ag, its production method, and an oxide superconducting conductor base material.
The inventors of the present invention conducted the following test in order to investigate the cause of being unable to obtain a high Jc value with a superconducting conductor using an oriented Ag base material during completion of the oxide superconducting conductor and its production method of the present invention. Although the oriented Ag base material is promising with respect to allowing the production of an oxide superconducting conductor at low costs, it had the disadvantage of not allowing the obtaining of adequate current density (Jc).
(1) After producing an oxide superconducting conductor by forming a YBaCuO-based superconducting layer having a thickness of 1.0 xcexcm on a pure Ag base material measuring 10 mm (W)xc3x9710 mm (L)xc3x970.5 mm (t) by CVD, and the removing only the oxide superconductor layer of the sample by etching, the amounts of the elements Y, Ba and Cu contained in the pure Ag base material were analyzed, and a comparison was made with the contents of each element in the pure Ag base material prior to deposition. Those results are shown in Table 1. As shown in Table 1, the Cu content of the pure Ag base material after formation of the oxide superconductor layer had clearly increased significantly. This is thought to be due to the Cu contained in the YBaCuO that composes the oxide superconductor layer having reacted by diffusing in the pure Ag base material.
(2) Next, a detailed analysis was conducted on the surface of the sample from which the above oxide superconductor layer had been removed. As a result, in the Ag base material after formation of the oxide superconductor layer, the Cu concentration at the Ag crystal grain boundary of the surface had increased in particular. Namely, elementary Cu diffused on the side of the Ag base material was determined to have preferentially precipitated or diffused at the crystal grain boundary of the Ag.
Based on the above tests (1) and (2), the inventors of the present invention concluded that there is the possibility that the superconductor characteristics of oxide superconducting conductors deteriorate due to the effects of Cu diffused in the Ag base material from the oxide superconductor layer, and found that it is necessary to pay attention to the following matters when producing a YBaCuO-based oxide superconducting conductor using Ag for the base material.
(1) Diffusion of elementary Cu at the interface between the Ag base layer and oxide superconductor layer should be suppressed.
(2) Grain boundary growth on the surface of the Ag base material should be suppressed and a smooth base material surface should be maintained.
In order to satisfy the conditions of (1) and (2) above, a study was conducted involving the initial formation of a layer containing Cu prior to the oxide superconductor layer on the surface layer of the Ag base material. Namely, by forming a layer in which Cu is diffused in advance on the surface of the Ag base material, the surface of the Ag base material can be made to contain a suitable concentration of Cu, (1) thereby making it possible to alleviate the diffusion of elementary Cu into the Ag base material. In addition, as a result, this was found to (2) suppress grain boundary growth on the surface of the base material and make it possible to maintain the smoothness of the base material surface, thereby leading to completion of the present invention. In addition, the inventors found that increasing the Cu concentration of the oxide superconductor layer in the vicinity of the interface between the base material and oxide superconductor layer could be used as a constitution that satisfies the requirements of (1) and (2) above, thereby leading to completion of the present invention.
The oxide superconducting conductor of the present invention is an oxide superconducting conductor having an oxide superconductor layer obtained by a method in which a raw material gas of an oxide superconductor is chemically reacted on at least one side of a base material containing Ag and deposited on the above base material, wherein a diffusion layer in which Cu is diffused in Ag is formed on the surface layer on the oxide superconductor layer side of the above base material, and the above oxide superconductor layer is formed on said diffusion layer.
Namely, by forming a diffusion layer in which Cu is diffused in the surface layer of an Ag base material in advance, the diffusion of Cu into the Ag base material from the oxide superconductor layer can be suppressed, and since grain boundary growth on the surface of the Ag base material can also be suppressed, there is no disturbance of the alloy composition of the oxide superconductor layer and no impairment of crystal continuity, thereby allowing the obtaining of an oxide superconducting conductor having superior superconductor characteristics.
In the oxide superconducting conductor of the present invention, the above base material is preferably composed of pure Ag. As a result of employing this constitution, the degree of accumulation (degree of orientation of Ag crystals) of the texture formed by rolling and heat treatment can be improved more than that of a base material that uses an alloy in which a second element is added to the Ag. Consequently, the crystal orientation of the oxide superconductor layer formed on this base material can be improved, and an oxide superconducting conductor can be provided having superior superconductor characteristics.
Next, the oxide superconducting conductor of the present invention is characterized by being provided with an oxide superconducting conductor base material provided with a base metal in the form of a tape and an Ag layer having a rolling texture formed on at least one side of said base metal, a diffusion layer formed by diffusing Cu in the surface layer of the Ag layer of the above base material, and an oxide superconductor layer formed on the above diffusion layer.
Namely, the oxide superconducting conductor of the present invention considerably improves strength more than conventional Ag base materials by using a base material having a two-layer structure provided with an Ag layer having a rolling texture on a base metal. In addition, since the diffusion of Cu from the oxide superconductor layer into the Ag base material can be effectively suppressed by forming a diffusion layer in which Cu is diffused in the surface layer of the Ag layer, resulting grain boundary growth of the oxide superconductor layer on the surface of the Ag base material can also be suppressed, thereby eliminating disturbance of the composition of the oxide superconductor layer and impairment of crystal continuity, and making it possible to obtain an oxide superconducting conductor having superior superconductor characteristics.
Next, the oxide superconducting conductor of the present invention is characterized by being an oxide superconducting conductor comprising the sequential generation of a plurality of layers of an oxide superconductor containing Cu by CVD on a base material for forming an oxide superconductor provided with an Ag layer having a rolling texture formed on at least one side of an Ag base material or other base metal, wherein among the above plurality of oxide superconductor layers, the Cu content of the oxide superconductor layer immediately above the base material is made to have a higher concentration than the Cu content of the other oxide superconductor layers.
Since the oxide superconductor layer directly above the Ag of the base material is generated by supplying a Cu raw material composition in excess, the multi-layer oxide superconducting conductor containing Cu of the present invention allows the obtaining of an oxide superconductor layer of the target composition even if elementary Cu is diffused in the Ag of the above base material, and the oxide superconductor layers sequentially generated thereon can also be made to be an oxide superconducting conductor having an oxide superconductor of the target composition.
Next, the oxide superconducting conductor of the present invention is preferably composed such that the Cu content of the above diffusion layer is from 50 xcexcg/cm2 to 300 xcexcg/cm2. As a result of employing this constitution, diffusion of Cu from the oxide superconductor layer can be effectively prevented. If the above Cu content is less than 50 xcexcg/cm2, the effect of suppressing the diffusion of Cu from the oxide superconductor layer is unable to be obtained, while in the case the Cu content exceeds 300 xcexcg/cm2, the Cu contained in the diffusion layer reacts with oxygen gas during formation of the oxide superconductor layer, resulting in its precipitation in the form of CuO and other oxides, thereby making this undesirable.
Next, the oxide superconducting conductor of the present invention is preferably composed such that the thickness of the above diffusion layer is within the range of 100 nm to 300 nm. Employing such a constitution enables the crystal orientation and crystal continuity of the oxide superconductor layer to be improved, making it possible to provide an oxide superconducting conductor having superior superconductor characteristics. In the case the thickness of the above diffusion layer is less than 100 nm, diffusion of Cu from the oxide superconductor layer cannot be prevented due to the insufficient amount of Cu contained in the diffusion layer, while if the thickness exceeds 300 nm, the excess Cu reacts with oxygen gas used during formation of the oxide superconductor layer resulting in precipitation of CuO and other oxides, thereby making this undesirable.
Next, in the oxide superconducting conductor of the present invention, the thickness of the above Ag layer is preferably within the range of 10 xcexcm to 100 xcexcm. If the thickness of the Ag layer is less than 10 xcexcm, the composite elements of the base metal are diffused into the superconducting layer through the Ag layer, making this undesirable. In addition, in the case the thickness exceeds 100 xcexcm, the amount of Ag used becomes large resulting in high cost of the base material, which is also undesirable.
Next, the oxide superconducting conductor of the present invention can also be composed to be provided with a barrier layer between the above Ag layer and base metal. Since the use of this constitution makes it possible to suppress the diffusion of elements that compose the base metal into the Ag layer and oxide superconductor layer, the texture of the Ag layer and the crystal structure of the oxide superconductor layer can be favorably maintained, thereby making it possible to obtain satisfactory crystal orientation and crystal continuity of the oxide superconductor layer formed on the Ag layer.
In addition, the oxide superconducting conductor provided with the above barrier layer can be composed such that the thickness of the above Ag layer is from 5 xcexcm to 10 xcexcm. Namely, the above barrier layer is able to prevent the diffusion of elements that compose the base metal into the Ag layer and oxide superconductor layer formed on the Ag layer. Thus, according to the present constitution, an oxide superconductor layer provided with satisfactory crystal continuity can be formed even if the Ag layer is thin, thereby making it possible to provide an oxide superconducting conductor having superior superconductor characteristics. In addition, if the thickness of the Ag layer in this oxide superconducting conductor equipped with a barrier layer is less than 5 xcexcm, it becomes difficult to laminate the Ag layer (Ag foil) to the barrier layer, thereby making this impractical. In addition, if the thickness exceeds 10 xcexcm, this leads to an increase in the cost of the base material, thereby making this undesirable.
Next, in the oxide superconducting conductor as claimed in the present invention, the Cu content of the oxide superconductor layer directly above the base material preferably has a concentration that is no more than 19% higher than the Cu content of the other oxide superconductor layers. Here, no higher than 19% means that the excess amount of Cu is greater than 0% but equal to or less than 19%. As a result of employing this constitution, an oxide superconductor layer having a prescribed composition can be formed on an oxide superconductor layer having a high Cu concentration, thereby allowing the obtaining of superior superconductor characteristics. If the above difference in Cu content exceeds 19%, the excess amount of Cu causes the occurrence of different phases such as CuO in the oxide superconductor layer, which is not desirable since it tends to cause deterioration of superconductor characteristics.
Next, the oxide superconducting conductor base material of the present invention is a base material in the form of a tape for composing an oxide superconducting conductor by chemically reacting a raw material gas of an oxide superconductor on at least one side to form an oxide superconductor layer, and is characterized by being provided with an Ag layer comprised of a base metal in the form of a tape and Ag having a rolling texture formed on at least one side of said base metal, the thickness of the above Ag layer being from 10 xcexcm to 100 xcexcm.
Namely, the oxide superconducting conductor base material of the present invention solves the problem of strength that was a problem of conventional Ag base materials by employing a duplex structure in which a layer composed of Ag is formed on a base metal. In addition, since technology used in the production of conventional clad materials can be applied for the technology for depositing or laminating the Ag on the base metal, a high-strength base material can be obtained inexpensively, thereby allowing the production of an oxide superconductor without impairing the advantages of the Ag base material.
Next, the oxide superconducting conductor base material of the present invention is a base material in the form of a tape for composing an oxide superconducting conductor by chemically reacting a raw material gas of an oxide superconductor on at least one side to form an oxide superconductor layer, and is characterized by being provided an Ag layer composed of a base metal in the form of a tape and Ag having a rolling texture formed on at least one side of said base metal, and a barrier layer formed between the above base metal and Ag layer, the thickness of the above Ag layer being from 5 xcexcm to 10 xcexcm.
Employing a constitution provided with a barrier layer between the base metal and Ag layer of the above base material makes it possible to suppress diffusion to the Ag layer side caused by heat treatment for introducing a rolling texture into the Ag layer and heating for forming the oxide superconductor layer. Thus, since the use of the oxide superconducting conductor base material of the present constitution makes it possible to prevent impairment of crystal orientation and crystal continuity of the oxide superconductor layer caused by such diffusion, an oxide superconducting conductor can be realized having superior superconductor characteristics.
Next, the production method of an oxide superconducting conductor of the present invention is a production method of an oxide superconducting conductor in which an oxide superconductor layer is generated on a base material by a method in which a raw material gas of an oxide superconductor is chemically reacted on at least one side of abase material, wherein a diffusion layer containing Cu is deposited on the above base material, and the above oxide superconductor layer is deposited on the above diffusion layer.
As a result of employing this constitution, the diffusion of Cu from the oxide superconductor layer to the Ag base material is suppressed, thereby allowing an oxide superconducting conductor having superior superconductor characteristics to be easily produced. In addition, the diffusion layer containing Cu can be formed easily by ordinary sputtering, vapor deposition or CVD and so forth without requiring the use of sophisticated and expensive film deposition technology for film deposition as in polycrystalline intermediate layers such as YSZ. Thus, according to the present constitution, an oxide superconducting conductor having superior superconductor characteristics can be produced inexpensively.
Next, the production method of an oxide superconducting conductor of the present invention is contains a step in which a diffusion layer in which Cu is diffused is formed on the surface layer of an Ag layer of an oxide superconducting conductor base material provided with a base metal and an Ag layer having a rolling texture formed on at least one side of said base metal, and a step in which an oxide superconductor layer is deposited on said diffusion layer by chemically reacting a raw material gas of an oxide superconductor.
As a result of employing this constitution, the diffusion of Cu from the oxide superconductor layer to the Ag base material is suppressed by the action of the above diffusion layer, and an oxide superconducting conductor having superior superconductor characteristics can be easily produced. In addition, the diffusion layer in which Cu is diffused can be formed easily by ordinary sputtering, vapor deposition or CVD and so forth without requiring the use of sophisticated and expensive film deposition technology for film deposition as in polycrystalline intermediate layers such as YSZ. Thus, according to the present constitution, an oxide superconducting conductor having superior superconductor characteristics can be produced inexpensively.
Next, the production method of an oxide superconducting conductor as claimed in the present invention comprises the generation of an oxide superconductor containing Cu while supplying a composition of a raw material solution of a reaction generation chamber for generating the above oxide superconductor directly on a base material so that the Cu composition is in greater excess than the above oxide superconductor composition, in the generation of a plurality of layers of oxide superconductor containing Cu by CVD on an oxide superconducting conductor base material provided with an Ag layer having a rolling texture formed on at least one side of an Ag base material or other base metal.
According to the production method of an oxide superconducting conductor of the present invention, since a YBaCuO-based superconductor formed directly on at least a base material is generated by supplying a raw material solution composition of a YBaCuO superconductor with the concentration of the Cu raw material in excess, the composite ratio of each element of the YBaCuO-based oxide superconductor layer formed on the oxide superconductor layer having a high Cu concentration can be made to be the composite ratio of a target prescribed YBaCuO-based oxide superconductor. In other words, as a result of making the elementary Cu in the raw material solution to be in excess, even if the above elementary Cu in the raw material solution is diffused in the Ag, since the Cu is made to be in excess in advance, the decrease is adequately compensated thereby allowing the production of an oxide superconducting conductor having a high Jc value and superior superconductor characteristics without disturbing the composition of the oxide superconductor and without impairing crystal continuity.
Next, in the production method of the oxide superconducting conductor, the above diffusion layer is preferably deposited to a layer thickness of 100 nm to 300 nm. As a result of employing this constitution, a suitably controlled diffusion layer can be formed, thereby allowing the production of an oxide superconducting conductor having even more superior superconductor characteristics.
Next, in the production method of an oxide superconducting conductor as claimed in the present invention, it is preferable to use an Ag base material having a rolling texture of a (110) orientation for the above base material. As a result of employing this constitution, a satisfactory crystal orientation can be obtained for the oxide superconductor layer formed on the base material, thereby allowing the production of an oxide superconducting conductor provided with superior superconductor characteristics. The above rolling texture of (110) orientation should be at least formed on the surface of the base material.
Next, in the production method of an oxide superconducting conductor as claimed in the present invention, at least two of the above reaction generation chambers are arranged in series, the composition of the above raw material solution of the above reaction generation chamber for generating the above oxide superconductor directly on the above base material is supplied so that the Cu composition is in greater excess than the composite ratio of the above oxide superconductor, and the raw material solution composition in the remaining reaction generation chamber is made to have a Cu composition that allows the obtaining of a prescribed oxide superconductor composition that is not the Cu composition of the reaction generation chambers that generates directly above the base material.
As a result of employing this constitution, an oxide superconductor layer having a high Cu concentration can be formed directly above the base material, and an oxide superconductor layer having a prescribed composite ratio can be formed on this oxide superconductor layer having a high Cu concentration.
Next, in the production method of an oxide superconducting conductor as claimed in the present invention, the Cu composition in the above reaction generation chamber for generating an oxide superconductor layer directly on the above base material preferably has a concentration that is 1-20% higher than the Cu composition in the other reaction generation chamber.
By making the Cu raw material composition that generates an oxide superconductor layer formed directly above the above Ag base material have a concentration that is within the range of 1-20% higher than the Cu raw material composition that generates an oxide superconductor layer formed thereafter, not only the oxide superconductor layer directly above the Ag base material, but also the entire oxide superconductor layer can be formed to a target composition. If the higher concentration of the above Cu raw material composition is higher by less than 1%, elementary Cu ends up diffusing in the Ag base material, and if it is higher by more than 20%, the elementary Cu becomes excessive, causing the generation of a different phase such as CuO in the oxide superconductor layer, resulting in the occurrence of the problem of being unable to obtain the target oxide superconductor. In addition, by generating an oxide superconductor with the Cu raw material composition in excess by 1-20%, an oxide superconductor layer can be obtained having a high Cu content at a concentration of 19% or less on the Ag base material.
Next, in the production method of an oxide superconducting conductor as claimed in the present invention, the thickness of the Ag layer of the above base material for forming the oxide superconductor is preferably from 10 xcexcm to 100 xcexcm. If the thickness of the Ag layer is less than 10 xcexcm, the composite elements of the base metal diffuse into the oxide superconductor layer through the Ag layer, which is not desirable. In addition, if the thickness of the Ag layer exceeds 100 xcexcm, the amount of Ag used becomes large, which is also undesirable since it results in increased cost of the base material.
Next, in the production method of an oxide superconducting conductor as claimed in the present invention, a barrier layer can also be formed between the above Ag layer of the above base material for forming the oxide superconductor, and the above base metal.
As a result of employing this constitution, since the elements that compose the base metal can be suppressed from diffusing into the Ag layer and oxide superconductor layer, the texture of the Ag layer and the crystal structure of the oxide superconductor layer can be favorably maintained, the oxide superconductor layer formed on the Ag layer can be made to have satisfactory crystal orientation and crystal continuity.
Moreover, in the production of an oxide superconducting conductor provided with the above barrier layer, the thickness of the above Ag layer is preferably from 5 xcexcm to 10 xcexcm. As a result of making the thickness within the above range, the elements that compose the base metal can be prevented from diffusing into the Ag layer and oxide superconductor layer formed on this Ag layer by the above barrier layer. Thus, according to the present constitution, an oxide superconductor layer provided with satisfactory crystal continuity can be formed even if the Ag layer is thin, and an oxide superconducting conductor can be produced in particular that has a high Jc value and superior superconductor characteristics. In addition, if the thickness of the Ag layer in this oxide superconducting conductor provided with a barrier layer is less than 5 xcexcm, it becomes difficult to laminate the Ag layer (Ag foil) to the barrier layer, thereby making this impractical. In addition, if the thickness exceeds 10 xcexcm, this leads to an increase in the cost of the base material, thereby making this undesirable.
Next, in the production method of an oxide superconducting conductor as claimed in the present invention, a protective layer composed of a precious metal material can also be formed on the above oxide superconductor layer. As a result of employing this constitution, the oxide superconductor layer can be stabilized, and there is less susceptibility to the occurrence of deterioration of the oxide superconductor layer caused by external effects, thereby allowing the production of an oxide superconducting conductor having superior reliability and a long service life.
Next, in the production method of an oxide superconducting conductor as claimed in the present invention, the above oxide superconductor layer can also be composed from a YBaCuO-based oxide superconductor. The production as claimed in the present invention is a particularly preferable method for the production of an oxide superconducting conductor having a YBaCuO-based superconductor layer.
Next, in the production method of an oxide superconducting conductor as claimed in the present invention, a reactor that carries out a CVD reaction that forms an oxide superconducting thin film by chemically reacting a raw material gas of an oxide superconductor on at least one side of a moving base material in the form of a tape, an oxide superconductor raw material gas supply means that supplies oxide superconductor raw material gas to the above reactor, and a gas exhaust means that evacuates the gas inside the above reactor; an oxide superconductor raw material gas supply source, an oxide superconductor raw material gas feed tube, and an oxygen gas supply means that supplies oxygen gas are provided in the above oxide superconductor raw material gas supply means; and in the above reactor, the base material feed section, reaction generation chambers and base material discharge section are respectively separated by diaphragms, a plurality of the above reaction generation chambers are provided in series in the direction of movement of the above base material tape, base material through holes are formed in each of the above diaphragms, a base material transport region is formed within the above reactor that passes through the base material feed section, the plurality of reaction generation chambers and the base material discharge section, gas diffusion sections are provided in each of the above plurality of reaction generation chambers, the above plurality of reaction generation chambers are made to be deposition regions, and deposition can be carried out by using a deposition apparatus comprised by the above oxide superconductor raw material gas feed tube being connected to said reaction generation chambers via the above gas diffusion section.
As a result of employing this constitution, since the above diffusion layer and oxide superconductor layer or oxide superconductor layer having a multi-layer structure can be deposited continuously, production of oxide superconducting conductors can be carried out more efficiently. Consequently, product yield can be improved and production costs can be reduced. In addition, if production is carried out by assigning the above plurality of reaction generation chambers to a reaction generation chamber for forming a diffusion layer and a reaction generation chamber for forming an oxide superconductor layer, these layers can be formed continuously, thereby allowing production of oxide superconducting conductors to be carried out more efficiently.
Since the oxide superconducting conductor of the present invention is composed by providing a diffusion layer containing Cu between a base material containing Ag and an oxide superconductor layer, diffusion of Cu from the oxide superconductor layer to the Ag base material can be suppressed, and as a result, grain boundary growth on the surface of the Ag base material can also be suppressed, thereby making it possible to obtain an oxide superconducting conductor having superior superconductor characteristics without disturbing the composition of the oxide superconductor layer and without impairing crystal continuity.
Next, according to the present invention, as a result of being composed by providing a base metal, an oxide superconducting conductor base material provided with an Ag layer having a rolling texture formed on at least one side of said base metal, a diffusion layer formed diffusing Cu in the surface layer of the Ag layer of the above oxide superconducting conductor, and an oxide superconductor layer formed on the above diffusion layer, an oxide superconducting conductor can be provided having superior strength and superconductor characteristics.
Next, since the production method of an oxide superconducting conductor of the present invention is made to deposit a diffusion layer containing Cu on an Ag base material, and deposit the above oxide superconductor layer on that diffusion layer, the diffusion of Cu from the oxide superconductor layer to the Ag base material is suppressed, allowing an oxide superconducting conductor having superior superconductor characteristics to be manufactured easily. In addition, the above diffusion layer containing Cu can be easily formed by ordinary sputtering, vapor deposition or CVD and so forth without requiring the use of sophisticated and expensive deposition technology as in a polycrystalline intermediate layer of YSZ and so forth. Thus, according to the present invention, an oxide superconducting conductor having superior superconductor characteristics can be produced inexpensively.
Next, since the oxide superconducting conductor of the present invention uses a base material in which an Ag layer having a rolling texture is formed on an Ag base material that is a material for forming an oxide superconductor or base metal having superior strength and so forth, and forms an oxide superconductor layer having a high Cu content directly above this Ag layer, the oxide superconductor layers formed sequentially thereon allow the generation of an oxide superconductor of a target composition. Consequently, the resulting oxide superconducting conductor has superconductor characteristics consisting of a high Jc value, and can be used as an oxide superconducting conductor having superior strength and other characteristics as well.
Next, as a result of employing a constitution provided with a base metal in the form of a tape and an Ag layer composed of Ag having a rolling texture formed on at least one side of said base metal, the oxide superconducting conductor base material of the present invention solves the problem of strength that had been a problem associated with Ag base materials of the prior art. In addition, since technology for depositing or laminating Ag onto the base metal can apply technology used for the production of clad materials of the prior art, a high-strength base material can be obtained inexpensively, thereby allowing the production of oxide superconductors without impairing the advantages of the Ag base material.
Next, according to the production method of an oxide superconducting conductor of the present invention, together with using an oxide superconducting conductor base material in which an Ag layer having a rolling texture is formed on an Ag base material or base metal, since a constitution is employed in which a diffusion layer in which Cu is diffused is formed on the surface layer of the Ag layer of the base material, and an oxide superconductor layer is formed on this diffusion layer, the diffusion of Cu from the oxide superconductor layer to the Ag base material can be suppressed, and an oxide superconducting conductor having superior superconductor characteristics can be easily produced. Thus, according to the production method as claimed in the present invention, an oxide superconducting conductor having superior superconductor characteristics and high strength can be produced inexpensively.
In addition, in the production method of an oxide superconducting conductor of the present invention, since an oxide superconductor layer formed directly on the above Ag layer is composed to generate an oxide superconductor layer while supplying Cu in greater excess than the Cu composition of oxide superconductor layers sequentially formed thereon, even if elementary Cu is diffused in the Ag, since the shortage of Cu is adequately compensated by the elementary Cu supplied in excess, the generated oxide superconductor allows the production of an oxide superconducting conductor having superconductor characteristics consisting of a high Jc value, and particularly a Jc value of 100,000 A/cm2 or more.